Generic sunroof units are generally known from the prior art. Vehicles with a large glass roof can have sunroof units of this type and thus have, in addition to the usually quite large window arranged in the roof, a roller blind system which can at least partially cover this window for the purpose of providing shade for the vehicle interior.
From the prior art, designs are known in which both the vehicle window and the roller blind system, in particular its guide rails, are fitted independent of one another in the roof area of a vehicle, for example on a common module frame. it is however also known at least from internal prior art how to attach direct to the window a guide rail frame consisting of two longitudinally extending guide rails and two transversely extending cross-members connecting the guide rails to one another at the front and rear, such that the window with the roller blind system attached to it can be installed in a vehicle as a single easy to handle structural unit.
This direct attachment of the guide rails as part of a closed frame to the vehicle window is in many cases not ideal, since the cross-members connecting the guide rails are felt to be a disadvantage from an aesthetic viewpoint. This is particularly so when the guide rails do not extend over the entire length of the window, but only over a part of the window, for example due to the use of several roller blind systems or for any other reason. In a case like this, the cross-members connecting the guide rails at the rear or front end would impair the intended unrestricted view through the sunroof to an unacceptable degree.
The maintenance of a defined distance between the two guide rails of a roller blind system, assured by the said cross-members in particular, is necessary since the flexible planar structures used in the stated application and whose lateral edge is guided by the guide rails, have to sag to a defined degree. It is therefore not acceptable when the distance between the guide rails decreases over the service life of a motor vehicle, as this increases the sag. The attachment of the guide rails to the vehicle window in a precisely defined way and not individualized for any single sunroof unit does permit the achievement of a precisely defined and constant distance, but it has proved that lack of constancy in the material properties of the planar structure make it necessary to provide, individually for each sunroof unit, a specific distance between the guide rails.